Edge protection seal for bonded substrates

ABSTRACT

A dielectric material layer is deposited on exposed surfaces of a bonded structure that includes a first substrate and a second substrate. The dielectric material layer is formed on an exposed planar surface of a second substrate and the entirety of peripheral sidewalls of the first and second substrates. The dielectric material layer can be formed by chemical vapor deposition, atomic layer deposition, or plasma induced deposition. Further, the dielectric material layer seals the entire periphery of the interface between the first and second substrates. If a planar portion of the dielectric material layer can be removed by planarization to facilitate thinning of the bonded structure, the remaining portion of the dielectric material layer can form a dielectric ring.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.13/556,369 filed on Jul. 24, 2012, which is a continuation of U.S.patent application Ser. No. 12/608,363, filed on Oct. 29, 2009, theentire content and disclosure of which are incorporated herein byreference.

BACKGROUND

This invention relates to a bonded structure having a peripheral sealingsidewall and methods of manufacturing the same.

Bonding of multiple substrates is required to enable three-dimensionalintegration of wafers. Because typical substrates have a tapered orrounded surface at the periphery, which is referred to as the bevelregion, the contact between two bonded substrates is limited to an areathat excludes the periphery of the substrates. The taper or rounding ofthe surfaces may be caused, for example, by lack of masking on theperipheral area of a substrate during an etch, or by a chuck thatpresses the substrate down during deposition, or inherent incomingsubstrate geometry includes a beveled substrate edge, thereby blockingdeposition of material on the peripheral area.

Through-substrate-via (TSV) structures, formed after multiple substratesare bonded and optionally thinned, provide electrical connection acrossthe multiple substrates in a bonded structure. A TSV structure includesa conductive material such as copper or tungsten.

Between the step of bonding of two substrates and the step of formationof TSV structures, one or both of the substrates in the bonded structuremay be thinned to facilitate formation of TSV structures. The thinningprocess employs slurries for planarization and generates particles ofthe material removed from the substrate(s) of the bonded structure. Suchmaterials generated or applied during the thinning process tend to getinto the space at the interface between two bonded substrates. Thus,semiconductor devices at the interface of a bonded structure may besubjected to such materials during the thinning process.

Further, the bonded structure may be subjected to wet processing steps,such as wet etching or a wet clean, that are intended to treat exposedbackside surfaces and/or surfaces within through substrate cavitieswithin the bonded structure. During such wet processing steps, however,semiconductor structures and materials at the interface between thebonded substrates can be exposed to a wet chemical that seeps in fromthe periphery of the bonded substrates. Thus, semiconductor devices andmaterials at the interface of a bonded structure may be subjected anunintentional exposure to wet chemicals employed in processing stepsafter bonding.

BRIEF SUMMARY

In an embodiment of the present invention, a dielectric material layeris deposited on exposed surfaces of a bonded structure that includes afirst substrate and a second substrate. The dielectric material layer isformed on an exposed planar surface of a second substrate and theentirety of peripheral sidewalls of the first and second substrates. Thedielectric material layer can be formed by chemical vapor deposition,atomic layer deposition, or plasma induced deposition. Further, thedielectric material layer seals the entire periphery of the interfacebetween the first and second substrates. If a planar portion of thedielectric material layer can be removed by planarization to facilitatethinning of the bonded structure, the remaining portion of thedielectric material layer can form a dielectric ring.

According to an aspect of the present invention, a bonded structure isprovided, which includes a first substrate having a first bonding-sidesurface and a first backside surface; a second substrate having a secondbonding-side surface and a second backside surface, wherein the secondsubstrate is bonded to the first substrate through a direct contactbetween the first bonding-side surface and the second bonding-sidesurface; and a dielectric material layer laterally contacting a firstsidewall surface at a periphery of the first substrate and a secondsidewall surface at a periphery of the second substrate and contiguouslyextending from the first backside surface to the second backsidesurface.

According to another aspect of the present invention, a method ofsealing a bonded structure is provided. The method includes bonding afirst substrate and a second substrate, wherein a first bonding-sidesurface of the first substrate is bonded to a second bonding-sidesurface of the second substrate at an interface; and forming adielectric material layer on a first sidewall surface at a periphery ofthe first substrate and a second sidewall surface at a periphery of thesecond substrate, wherein the dielectric material layer contiguouslyextends from a first backside surface of the first substrate to a secondbackside surface of the second substrate and seals the interface.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of a first exemplary structureafter bonding of a first substrate and a second substrate according to afirst embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of the first exemplarystructure after forming a dielectric material layer according to thefirst embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of a second exemplarystructure after forming a dielectric material layer according to asecond embodiment of the present invention.

FIG. 4 is a vertical cross-sectional view of a third exemplary structureduring deposition of dielectric material layer according to a thirdembodiment of the present invention.

FIG. 5 is a vertical cross-sectional of a fourth exemplary structureafter thinning of the second substrate by planarization according to afourth embodiment of the present invention.

FIG. 6 is a vertical cross-sectional of the fourth exemplary structureafter further thinning of the second substrate by a chemical etchingstep according to the fourth embodiment of the present invention.

FIG. 7 is a vertical cross-sectional view of the fourth exemplarystructure after a touch-up planarization according to the fourthembodiment of the present invention.

FIG. 8 is a vertical cross-sectional view of a fifth exemplary structureaccording to a fifth embodiment of the present invention.

FIG. 9 is a vertical cross-sectional view of a sixth exemplary structureaccording to a sixth embodiment of the present invention.

DETAILED DESCRIPTION

As stated above, the present invention relates to a bonded structurehaving a peripheral sealing sidewall and methods of manufacturing thesame, which are now described in detail with accompanying figures. Thedrawings are not necessarily drawn to scale.

As used herein, “sealing” a first element means forming a second elementon a surface of said first element to prevent exposure of a surface ofsaid first element to ambient conditions.

As used herein, “sidewall” refers to a region at the edge of thesubstrate, which is typically beveled.

As used herein, a “sealing sidewall” is a sidewall that provides asealing on an element.

As used herein, a “periphery” is a one-dimensional closed shape that maybe contiguously stretched or deformed to a circle without forming ordestroying a contact between any pair of points in the one-dimensionalclosed shape.

As used herein, a “peripheral sealing sidewall” is a sealing sidewallthat is located along a periphery of an element.

As used herein, a “bonding-side surface” of an element is a surface ofsaid element that is bonded to another element.

As used herein, a “backside surface” of an element is a surface of saidelement that is not bonded to another element.

As used herein, a “polymer” is a molecule synthesized through theprocess of polymerization of monomers and including repeating structuralunits connected by chemical bonds.

As used herein, a “polymer material” is a material composed of apolymer.

As used herein, a “non-polymer material” is a material that is notcomposed of a polymer.

As used herein, a “ring” is an element having a three-dimensional shapethat may be contiguously stretched or deformed to a torus withoutforming or destroying a contact between any pair of points in thethree-dimensional shape.

As used herein, an element is “ring-shaped” if the shape of said elementis a ring.

Referring to FIG. 1, a first exemplary structure according to a firstembodiment of the present invention includes a first substrate 100 and asecond substrate 200. The first substrate 100 includes a first substratelayer 10 and a first bonding layer 12. The second substrate 200 includesa second substrate layer 20 and a second bonding layer 22. Outersurfaces of the first substrate 100 include a first bonding-side surface11 that is the outer surface of the first bonding layer 12, a firstbackside surface 19 that is an exposed surface of the first substratelayer 10, and a first sidewall surface 15 that substantially normal tothe first bonding-side surface 11. Outer surfaces of the secondsubstrate 200 include a second bonding-side surface 21 that is the outersurface of the second bonding layer 22, a second backside surface 29that is an exposed surface of the second substrate layer 20, and asecond sidewall surface 25 that is substantially normal to the firstbonding-side surface 11. The second substrate 200 is bonded to the firstsubstrate 100 through a direct contact between the first bonding-sidesurface 12 and the second bonding-side surface 22.

Each of the first substrate layer 10 and the second substrate layer 20can include a semiconductor substrate, an insulator substrate, aconductor substrate, or a composite substrate including at least twosubstrates. In case the first and/or second substrate layer (10, 20)includes a semiconductor substrate, the semiconductor substrate includesa semiconductor material, which may be selected from, but is not limitedto, silicon, germanium, silicon-germanium alloy, silicon carbon alloy,silicon-germanium-carbon alloy, gallium arsenide, indium arsenide,indium phosphide, III-V compound semiconductor materials, II-VI compoundsemiconductor materials, organic semiconductor materials, and othercompound semiconductor materials. A semiconductor substrate, thesemiconductor substrate may, or may not, be a single crystallinesubstrate. At least one semiconductor device (not shown) can be presenton or in the semiconductor substrate. The at least one semiconductordevice can be, but is not limited to, a field effect transistor, abipolar transistor, a diode, a resistor, a capacitor, a varactor, aninductor, a carbon nanotube device, or any other type of semiconductordevice or a nanoscale device. The semiconductor substrate can include atleast one doped region (not shown) therein.

Further, each of the first and second substrates (100, 200) can includeat least one dielectric material layer (now shown). The at least onedielectric material layer includes at least one dielectric material,which can be a doped or undoped silicate glass, silicon nitride, a lowdielectric constant (low-k) chemical vapor deposition (CVD) materialsuch as organosilicate glass, a low-k spin-on dielectric material suchas SiLK™, BLoK™, NBLoK™, or any other type of dielectric material thatcan be deposited or formed on a substrate and able to hold at least onemetal pad therein. Further, at least one metal interconnect structure(not shown) can be embedded in the at least one dielectric materiallayer to provide electrical connection to the at least one semiconductordevice, if present, in the first or second substrates (100, 200).

The first bonding layer 12 and the second bonding layer 22 include amaterial that can be bonded. For example, the first and second bondinglayers (12, 22) can be a pair of copper layers, a pair of silicon oxideor other bonding dielectric layers, or a pair of patterned layer ofcopper and silicon oxide. In addition, any other bondable material canbe employed for the first bonding layer 12 and the second bonding layer,including but not limited to polymeric adhesive materials. The first andsecond bonding layers (12, 22) can have a thickness from 300 nm to30,000 nm, although lesser and greater thicknesses can also be employed.

The first bonding-side surface 11 and the second bonding-side surface 21directly contact each other at a substantially planar plane, which is aninterface between the first substrate 100 and the second substrate 200.Due to rounding of the first bonding-side surface 11 and the secondbonding-side surface 21, the interface does not extend to the firstsidewall surface 15 or the second sidewall surface 25. Instead, theperiphery of the interface between the first bonding-side surface 12 andthe second bonding-side surface 22 is laterally recessed inward from thefirst sidewall surface 15 and the second sidewall surface 25. The firstbackside surface 19 and the second backside surface 29 can be parallelto the interface at which the first bonding-side surface 11 and thesecond bonding-side surface 21 contact each other.

The thickness of the first substrate 100 and the thickness of the secondsubstrate 200 can be from 50 microns to 1,000 microns, although lesserand greater thicknesses can also be employed. In case the firstsubstrate 100 and the second substrate 200 have a circular horizontalcross-sectional area, the diameter of the first substrate 100 and thesecond substrate 200 can be from 50 mm to 300 mm, although lesser andgreater diameters can also be employed.

Referring to FIG. 2, a dielectric material layer 30 is formed on thesecond backside surface 29, the first sidewall surface 15, the secondsidewall surface 25, the portion of the first bonding-side surface 12that does not contact the second bonding-side surface 22, and theportion of the second bonding-side surface 22 that does not contact thefirst bonding-side surface 12. In one embodiment, the dielectricmaterial layer 30 is formed by placing the bonded structure includingthe first and second substrates (100, 200) on a chuck and depositing adielectric material on the exposed surface of the bonded structure. Inthis case, the dielectric material is not intentionally deposited on thefirst backside surface 19, although some residual deposition may occuron first backside surface 19. In another embodiment, the dielectricmaterial layer 30 is formed by placing the bonded structure includingthe first and second substrates (100, 200) on a support structure thatcontacts only a portion of the first backside surface. In this case, thedielectric material layer 30 can be formed on a portion of the firstbackside surface 19 as well.

The dielectric material layer 30 laterally contacts the first sidewallsurface 15 at a periphery of the first substrate 100 and the secondsidewall surface 25 at a periphery of the second substrate 200. Thedielectric material layer 30 is a structure of unitary construction,i.e., a structure embodied in a single piece. Thus, the entirety of thedielectric material layer 30 is contiguous. The dielectric materiallayer 30 contiguously extends from the first backside surface 19 to thesecond backside surface 19 and covers the second backside surface 29.The dielectric material layer 30 is formed on the entirety of the secondbackside surface 29, the entirety of the first sidewall surface 15, andthe entirety of the second sidewall surface 25.

The dielectric material layer 30 contacts all portions of the firstbonding-side surface 12 that does not contact the second bonding-sidesurface 22 and all portions of the second bonding-side surface 22 thatdoes not contact the first bonding-side surface 12. The dielectricmaterial layer 30 contacts and laterally surrounds a periphery of theinterface between the first substrate 100 and the second substrate 200.

The dielectric material layer 30 can be deposited by high density plasmachemical vapor deposition (HDPCVD) or plasma enhanced chemical vapordeposition (PECVD). Alternately, the dielectric material layer 30 can beformed by low pressure chemical vapor deposition (LPCVD), atomic layerdeposition (ALD), or sub-atmospheric chemical vapor deposition (SACVD).The dielectric material layer 30 can include an inorganic dielectricmaterial, an organic dielectric material, or a combination thereof.

In case the dielectric material layer 30 includes an inorganicdielectric material, the inorganic dielectric material can be any ofsilicon oxide, silicon nitride, silicon boride, silicon carbon nitride,a dielectric metal oxide, a dielectric metal nitride, a dielectric metalsilicate, and combinations thereof. The silicon oxide can be an undopedsilicate glass (USG), or a doped silicate glass such as fluorodilicateglass (FSG), borosilicate glass (BSG), arsenosilicate glass (ASG),phosphosilicate glass (PSG), and borophosphosilicate glass (BPSG). Thedielectric metal oxide and the dielectric metal nitride can be an high-kdielectric material such as HfO₂, ZrO₂, La₂O₃, Al₂O₃, TiO₂, SrTiO₃,LaAlO₃, Y₂O₃, HfO_(x)N_(y), ZrO_(x)N_(y), La₂O_(x)N_(y), Al₂O_(x)N_(y),TiO_(x)N_(y), SrTiO_(x)N_(y), LaAlO_(x)N_(y), Y₂O_(x)N_(y), and an alloythereof. Each value of x is independently from 0.5 to 3 and each valueof y is independently from 0 to 2. The dielectric metal silicate can bea silicate of any of the dielectric metal oxide and the dielectric metalnitride.

In case the dielectric material layer 30 includes an organic dielectricmaterial, the dielectric material layer 30 can be a polymer material ora non-polymer material. The dielectric material layer 30 can be composedof a material selected from silicon carbide, silicon carbon boride, oran organic polymer.

If the dielectric material layer 30 is deposited by high density plasmachemical vapor deposition (HDPCVD) or plasma enhanced chemical vapordeposition (PECVD), the dielectric material layer 30 is depositednon-conformally. In this case, a first thickness t1 of the dielectricmaterial layer 30 on the second backside surface 29 is greater than asecond thickness t2 of the dielectric material layer 30 on the first andsecond sidewall surfaces (15, 25) because more dielectric material isdeposited on the second backside surface 29 than on the first and secondsidewall surfaces (15, 25) of the first and second substrates (100,200).

The second thickness t2 of the dielectric material layer can be from 100nm to 3,000 nm, although lesser and greater thicknesses are alsocontemplated herein. If the second thickness t2 exceeds one half of themaximum separation distance between the first bonding-side surface 11and the second bonding-side surface 12, all space between the firstbonding-side surface 11 and the second bonding-side surface is filledwith the dielectric material layer 30. The maximum separation distancebetween the first bonding-side surface 11 and the second bonding-sidesurface 12 is typically from 1 micron to 3 microns, although lesser andgreater maximum separation distances can also be employed depending onthe planarity of the first and second bonding-side surfaces (11, 21).

Referring to FIG. 3, a second exemplary structure according to a secondembodiment of the present invention includes a dielectric material layer30 that can be formed employing the same methods as in the firstembodiment. In the second embodiment, the second thickness t2 of thedielectric material layer 30 is less than the maximum separation betweenthe first bonding-side surface 11 and the second bonding-side surface12. Thus, the dielectric material layer 30 does not completely fill aperipheral gap between the first substrate 100 and the second substrate200.

The dielectric material layer 30 includes a laterally recessed portion40 at a periphery of the interface between the first bonding-sidesurface 11 and the second bonding-side surface 21. The outer surface ofthe dielectric material layer 30 is recessed inward toward the interfaceat the laterally recessed portion 40. The peripheral gap is present inthe laterally recessed portion 40 between a portion of the dielectricmaterial layer 30 on the first bonding-side surface 11 and a portion ofthe dielectric material layer 30 on the second bonding-side surface 21.The laterally recessed portion 40 laterally encircles the interface.

Referring to FIG. 4, a third exemplary structure according to a thirdembodiment of the present invention includes a bonded structure of afirst substrate 100 and a second substrate 200 that is placed in aplasma deposition chamber. The plasma deposition chamber includes anenclosure 140, a chuck 110, and a focus ring 120. The bonded structureof the first substrate 100 and the second substrate 200 is placed on thechuck 110 such that the first backside surface 19 contacts a top surfaceof the chuck 110. The inside of the enclosure is maintained in a vacuumenvironment at a pressure less than 10 mTorr, and typically less than0.1 mTorr.

A reactant gas including a precursor material for the dielectricmaterial layer 30 is introduced into the process chamber through atleast one opening (not shown) in the enclosure. The pressure in theenclosure 140 is maintained in a range from 0.1 mTorr to 10 mTorr, and aradio frequency (RF) power is applied to generate a plasma in theenclosure 140. The reactant gas is decomposed to generate a monomer,which is subsequently polymerized upon deposition on the bondedstructure of the first substrate 100 and the second substrate 200. Forexample, the reactant gas can be C₄F₈, which generates a monomer of—CF₂—. The monomer is polymerized on the surfaces of the bondedstructure of the first substrate 100 and the second substrate 200 andconstitutes a dielectric material layer 30.

A polymer layer 130 is formed on the surfaces of the focus ring 120. Thepolymer layer 130 has the same polymeric material as the dielectricmaterial layer 30, i.e., the polymer material that is formed bypolymerization of the monomers. The plasma impinges on the polymer layer130 and sputters the material of the polymer layer 130 on the first andsecond sidewall surfaces (15, 25) of the first and second substrates(100, 200). The sputtered polymeric material from the polymer layer 130can be deposited between the first bonding-side surface 11 and thesecond bonding-side surface 21 to facilitate filling the gap between thefirst bonding-side surface 11 and the second bonding-side surface 21.

Other hydro-fluorocarbon feedstock reactant gases that can be employedinclude, but are not limited to, C_(x)F_(y), C_(x)H_(y)F_(z), SF₆, C₂H₄,N₂/H₂, and CH₄, combined with carrier gases such as He, Ar, and N₂.Monomers that can be derived from the reactant gas include, but are notlimited to, CF_(x), C_(x)H_(y), C_(x)N_(y)H_(z), and C_(x)H_(y)F_(z).The polymer material of the dielectric material layer 30 is formed bypolymerization of at least one monomer.

Referring to FIG. 5, a fourth exemplary structure according to a fourthembodiment of the present invention is derived from the first, second,or third exemplary structure of the present invention by thinning of thesecond substrate 200 by planarization. The second substrate 200 can bethinned, for example, by grinding, chemical mechanical planarization, achemical etch, or a combination thereof.

The portion of the dielectric material layer 30 above the secondbackside surface 29 of the second substrate 200 is removed. The secondbackside surface 29 is vertically recessed and moves toward the secondbonding-side surface 21 as the second substrate 200 is thinned. Thedielectric material layer 30′, which is formed by the remaining portionof the dielectric material layer 30 (See FIGS. 2-4) prior toplanarization, is a ring-shaped structure. The first and second backsidesurfaces (19, 29) do not contact a surface of the dielectric materiallayer 30′. An end surface of the ring-shaped structure of the dielectricmaterial layer 30′ can be coplanar with the first backside surface 19,and another end surface of the ring-shaped structure of the dielectricmaterial layer 30′ can be coplanar with the second backside surface 29.

Optionally, the first substrate 100 can be thinned as well by removingthe material of the first substrate 100 from the side of the firstbackside surface 19. The material of the first substrate 100 can beremoved, for example, by grinding, chemical mechanical planarization, achemical etch, or a combination thereof.

Through-substrate vias (not shown) can be formed through the first andsecond substrates (100, 200) by forming deep trenches and depositing adielectric liner material and a conductive material to fill the deeptrenches. Excess material outside the deep trenches can be removed, forexample, by a recess etch or a planarization.

The ring-shaped structure of the dielectric material layer 30′ is aperipheral sealing sidewall for the first and second substrates (100,200) that provides a sealing of the interface between the firstbonding-side surface 11 and the second bonding-side surface 21. Wetclean processing steps can be employed during the formation of thethrough-substrate vias without concern about potential damage to thebonding between the first and second substrates (100, 200) because theinterface between the first bonding-side surface 11 and the secondbonding-side surface 21 is sealed by the ring-shaped structure of thedielectric material layer 30′.

Referring to FIG. 6, the fourth exemplary structure can be subjected toadditional thinning, which can be effected, for example, by a chemicaletching step. The second backside surface 29 can be vertically recessedby chemical mechanical planarization or an etch process relative to thering-shaped structure of the dielectric material layer 30′. The etch ofthe second substrate 200 from the second backside surface 29 can betimed. Alternately, the second substrate 20 can include a plurality oflayers having different compositions, and the etch of the secondsubstrate 200 from the second backside surface 29 can be a selectiveetch that stops on a surface of a layer having a composition that isresistant to the etchant employed in the etching process.

Referring to FIG. 7, the fourth exemplary structure can be subjected toa touch-up chemical mechanical planarization to remove a portion of thering-shaped structure of the dielectric material layer 30′ thatprotrudes above the second backside surface 29 or the first backsidesurface 19, if any of dielectric material layer 30′ remains. Additionalcleaning processes employing a wet chemical can be performed withoutaffecting the bonding between the first and second substrates (100,200).

Referring to FIG. 8, a fifth exemplary structure according to a fifthembodiment of the present invention can be derived from any of thefirst, second, and third exemplary structures by thinning the firstsubstrate 100. The first substrate 100 can be thinned, for example, bygrinding, chemical mechanical planarization, a chemical etch, or acombination thereof. Through substrate vias can be formed from the sideof the first backside surface 19. If a wet etching process is employed,the dielectric material layer 30 protects the interface between thefirst and second substrates (100, 200) by sealing the first sidewallsurface 15 and the second sidewall surface 25.

The processing steps of FIGS. 5-8 can be employed individually or incombination to effect formation of additional structural features in thebonded structure of the first substrate 100 and the second substrate200. The ring-shaped structure of the dielectric material layer 30′ asin FIGS. 5-7 or the dielectric material layer 30 as in FIG. 8 seals theportion of the first bonding-side surface 11 that does not contact thesecond bonding-side surface 21 and the portion of the secondbonding-side surface 21 that does not contact the first bonding-sidesurface 11. Thus, access of wet chemicals or dry etchants to theunbonded portions of the first and second bonding-side surfaces (11, 21)is prevented by the ring-shaped structure of the dielectric materiallayer 30′ or the dielectric material layer 30 during formation ofadditional structural features after the bonding of the first and secondsubstrates (100, 200).

Referring to FIG. 9, a sixth exemplary structure according to a sixthembodiment of the present invention can be derived from any of the firstthrough fifth exemplary structures by removing the ring-shaped structureof the dielectric material layer 30′ or the dielectric material layer 30that covers the second backside surface 29. The ring-shaped structure ofthe dielectric material layer 30′ or the dielectric material layer 30can be removed as needed, or can be used up during a long etch process.In this case, another dielectric material layer 70 can be formed on theexposed portions of the first and second bonding-side surfaces (11, 21),the first and second sidewall surfaces (15, 25), and one of the firstand second backside surfaces (19, 29) as need employing the same methodsas described above for formation of a dielectric material layer 30. Thematerial of the other dielectric material layer 70 is any material thatcan be employed for the dielectric material layer 30′ or the dielectricmaterial layer 30. Thus, the present invention allows repeated formationand removal of dielectric material layers which can be employed to sealportions of the first and second bonding-side surfaces (11, 21) that donot contact each other to form an interface. Each dielectric materiallaterally surrounds and seals the interface between the first and secondsubstrates (100, 200).

While the present invention has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details can be made without departing from the spirit and scope ofthe present invention. It is therefore intended that the presentinvention not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

What is claimed is:
 1. A method of sealing a bonded structurecomprising: bonding a first substrate and a second substrate, wherein afirst bonding-side surface of said first substrate is bonded to a secondbonding-side surface of said second substrate at an interface; forming adielectric material layer on a first sidewall surface at a periphery ofsaid first substrate and a second sidewall surface at a periphery ofsaid second substrate, wherein said dielectric material layercontiguously extends from a periphery of a first backside surface ofsaid first substrate to a second backside surface of said secondsubstrate and seals said interface; and thinning said second substrateby planarization.
 2. The method of claim 1, wherein said dielectricmaterial layer is formed directly on all portions of said firstbonding-side surface that does not contact said second bonding-sidesurface and all portions of said second bonding-side surface that doesnot contact said first bonding-side surface.
 3. The method of claim 1,wherein said dielectric material layer is formed directly on a peripheryof said interface, and said dielectric material layer laterallysurrounds said interface.
 4. The method of claim 1, wherein saiddielectric material layer is formed on an entirety of said secondbackside surface and an entirety of said first sidewall surface and saidsecond sidewall surface.
 5. The method of claim 1, further comprising:removing a portion of said dielectric material layer from above saidsecond backside surface; and vertically recessing said second backsidesurface by chemical mechanical planarization or an etch process.
 6. Themethod of claim 1, wherein an entirety of said dielectric material layeris contiguous, and said dielectric material layer contacts an entiretyof said second backside surface.
 7. The method of claim 1, wherein saiddielectric material layer is deposited non-conformally.
 8. The method ofclaim 7, wherein a first thickness of said dielectric material layer onsaid second backside surface is greater than a second thickness of saiddielectric material layer on said first and second sidewall surfaces. 9.The method of claim 1, wherein a remaining portion of said dielectricmaterial layer includes a surface that is coplanar with said secondbackside surface.
 10. The method of claim 1, wherein a remaining portionof said dielectric material layer does not overlie or underlie any areaof said direct contact between said first bonding-side surface and saidsecond bonding-side surface.
 11. The method of claim 1, wherein aremaining portion of said dielectric material layer forms a ring-shapedstructure.
 12. The method of claim 1, wherein said dielectric materiallayer has a same composition at every surface portion that contacts saidfirst substrate and said second substrate.
 13. The method of claim 1,wherein said dielectric material layer is deposited directly onperipheral regions of said first bonding-side surface that is not withina plane of said interface and peripheral regions of said secondbonding-side surface that is not within said plane of said interface.14. A method of sealing a bonded structure comprising: bonding a firstsubstrate and a second substrate, wherein a first bonding-side surfaceof said first substrate is bonded to a second bonding-side surface ofsaid second substrate at an interface; and forming a dielectric materiallayer on a first sidewall surface at a periphery of said first substrateand a second sidewall surface at a periphery of said second substrate,wherein said dielectric material layer contiguously extends from aperiphery of a first backside surface of said first substrate to asecond backside surface of said second substrate and seals saidinterface, wherein said dielectric material layer is deposited by highdensity plasma chemical vapor deposition (HDPCVD) or plasma enhancedchemical vapor deposition (PECVD).
 15. The method of claim 14, whereinan inorganic dielectric material is deposited to form said dielectricmaterial layer.
 16. The method of claim 15, wherein said dielectricmaterial layer is composed of a material selected from silicon oxide,silicon nitride, silicon boride, silicon carbon nitride, a dielectricmetal oxide, a dielectric metal nitride, a dielectric metal silicate,and combinations thereof.
 17. The method of claim 14, wherein an organicmaterial is deposited to form said dielectric material layer.
 18. Themethod of claim 17, wherein said dielectric material layer is composedof a material selected from silicon carbide, silicon carbon boride, anorganic polymer.
 19. The method of claim 14, further comprising:removing a portion of said dielectric material layer from above saidsecond backside surface; and vertically recessing said second backsidesurface by chemical mechanical planarization or an etch process.
 20. Amethod of sealing a bonded structure comprising: bonding a firstsubstrate and a second substrate, wherein a first bonding-side surfaceof said first substrate is bonded to a second bonding-side surface ofsaid second substrate at an interface; and forming a dielectric materiallayer on a first sidewall surface at a periphery of said first substrateand a second sidewall surface at a periphery of said second substrate,wherein said dielectric material layer contiguously extends from aperiphery of a first backside surface of said first substrate to asecond backside surface of said second substrate and seals saidinterface, wherein said dielectric material is composed of an organicpolymer in which a monomer of —CF₂— is polymerized.